The Applicant's earlier German Patent Application P 199 49 507.4 describes several transmission layouts for an automatic multiple-ratio transmission having various combinations of coupled planetary gear sets. By appropriate linkage of a non-shiftable front-mounted gear set combination to a shiftable rear-mounted gear set combination, at least seven forward speeds can be engaged in each case without group shifting. The number of shiftable forward speeds is at least two greater than the number of shifting elements. DE-P 199 49 507.4 proposes to embody the shiftable rear-mounted gear set as a two-carrier four-shaft transmission, exactly one shifting element being arranged on its first shaft, at least two on the second shaft, and exactly two on the third shaft. The fourth shaft of the two-carrier four-shaft transmission is connected to the output drive shaft of the transmission. In all variant embodiments of DE-P 199 49 507.4, it is also essential that a maximum of two shifting elements have the same rotation speed level.
A “two-carrier four-shaft transmission” is understood here to be an arrangement of two individual mechanically coupled single-carrier planetary gear sets in which as a result of a double component linkage, the coupled units have four so-called “free shafts,” in which context a “shaft” can be a sun gear, a ring gear, or also a carrier of a planetary gear set.
It is the object of the present invention, proceeding from the aforesaid existing art, to develop further a multiple-ratio transmission, having at least seven forward speeds shiftable without group shifting, in terms of comparatively reduced design complexity with no change in its favorable ratio spacing and wide spread.